/*
 * Copyright 2002-2012 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.core.style;

import java.lang.reflect.Method;
import java.util.Collection;
import java.util.Iterator;
import java.util.List;
import java.util.Map;
import java.util.Set;

import org.springframework.util.ClassUtils;
import org.springframework.util.ObjectUtils;

/**
 * Converts objects to String form, generally for debugging purposes,
 * using Spring's {@code toString} styling conventions.
 *
 * <p>Uses the reflective visitor pattern underneath the hood to nicely
 * encapsulate styling algorithms for each type of styled object.
 *
 * 默认的值格式化工具
 * 通常出于调试的目的，我们需要把对象用字符串的方式输出
 * 我们可以使用Spring默认的格式化工具
 *
 *
 * @author Keith Donald
 * @author Juergen Hoeller
 * @since 1.2.2
 */
public class DefaultValueStyler implements ValueStyler {

    private static final String EMPTY = "[empty]";
    private static final String NULL = "[null]";
    private static final String COLLECTION = "collection";
    private static final String SET = "set";
    private static final String LIST = "list";
    private static final String MAP = "map";
    private static final String ARRAY = "array";


    /**
     * 格式化一个普通对象
     *
     * @param value the Object value to style
     * @return
     */
    public String style(Object value) {
        if (value == null) {
            return NULL;
        } else if (value instanceof String) {
            return "\'" + value + "\'";
        } else if (value instanceof Class) {
            // 获取类的比较短的名称
            return ClassUtils.getShortName((Class) value);
        } else if (value instanceof Method) {
            Method method = (Method) value;
            return method.getName() + "@" + ClassUtils.getShortName(method.getDeclaringClass());
        } else if (value instanceof Map) {
            return style((Map) value);
        } else if (value instanceof Map.Entry) {
            return style((Map.Entry) value);
        } else if (value instanceof Collection) {
            return style((Collection) value);
        } else if (value.getClass().isArray()) {
            return styleArray(ObjectUtils.toObjectArray(value));
        } else {
            return String.valueOf(value);
        }
    }

    /**
     * 格式化映射
     *
     * @param value 映射
     * @return
     */
    private String style(Map value) {
        StringBuilder result = new StringBuilder(value.size() * 8 + 16);
        result.append(MAP + "[");
        for (Iterator it = value.entrySet().iterator(); it.hasNext();) {
            Map.Entry entry = (Map.Entry) it.next();
            result.append(style(entry));
            if (it.hasNext()) {
                result.append(',').append(' ');
            }
        }
        if (value.isEmpty()) {
            result.append(EMPTY);
        }
        result.append("]");
        return result.toString();
    }

    /**
     * 格式化键值对
     *
     * @param value 键值对
     * @return
     */
    private String style(Map.Entry value) {
        return style(value.getKey()) + " -> " + style(value.getValue());
    }

    /**
     * 格式化集合
     *
     * @param value 集合
     * @return
     */
    private String style(Collection value) {
        StringBuilder result = new StringBuilder(value.size() * 8 + 16);
        result.append(getCollectionTypeString(value)).append('[');
        for (Iterator i = value.iterator(); i.hasNext();) {
            result.append(style(i.next()));
            if (i.hasNext()) {
                result.append(',').append(' ');
            }
        }
        if (value.isEmpty()) {
            result.append(EMPTY);
        }
        result.append("]");
        return result.toString();
    }

    /**
     * 获取集合的类型
     *
     * @param value 集合
     * @return
     */
    private String getCollectionTypeString(Collection value) {
        if (value instanceof List) {
            return LIST;
        } else if (value instanceof Set) {
            return SET;
        } else {
            return COLLECTION;
        }
    }

    /**
     * 格式化数组
     *
     * @param array 数组
     * @return
     */
    private String styleArray(Object[] array) {
        StringBuilder result = new StringBuilder(array.length * 8 + 16);
        result.append(ARRAY + "<").append(ClassUtils.getShortName(array.getClass().getComponentType())).append(">[");
        for (int i = 0; i < array.length - 1; i++) {
            result.append(style(array[i]));
            result.append(',').append(' ');
        }
        if (array.length > 0) {
            result.append(style(array[array.length - 1]));
        } else {
            result.append(EMPTY);
        }
        result.append("]");
        return result.toString();
    }

}
